1. Field of the Invention
The present invention relates to a method for electrifying a plurality of electric conductors arranged on a substrate, and in particular relates an electrifying method capable of preventing cracks of the substrate produced by a temperature difference of the substrate during the electrifying. Furthermore, it relates to a manufacturing method and a manufacturing device of an electron-source substrate having a plurality of electron-emission elements as well as a manufacturing method of an image-forming apparatus on the basis of the electrifying method.
2. Description of the Related Art
Hitherto, as the electron-emission element, two kinds of elements using a thermal electron-emission element and a cold cathode electron-emission element are known as a general classification. The cold cathode electron-emission element generally includes a field emission type, a metal/insulting layer/metal type, and a surface-conduction electron-emission element.
The surface-conduction electron-emission element utilizes a phenomena that an electron is emitted by applying an electric current through a conductive film with a small area formed on a substrate in parallel with the film surface. The inventor has been made a number of proposals regarding to the surface-conduction electron-emission element and its application. For example, its basic structure and manufacturing method are disclosed in Japanese Patent Laid-Open No. 7-235255 and Japanese Patent Laid-Open No. 8-171849.
The surface-conduction electron-emission element disclosed in the above-mentioned Publications is characterized in that on a substrate, there are provided a pair of element electrodes opposing each other and a conductive film having an electron-emission portion disposed in part thereof and connected to the element electrodes. The conductive film is provided with a crack formed in part thereof. Also, at the end of the crack formed is a deposited film having at least one of carbon and a carbon compound as a principal ingredient.
By arranging a plurality of such electron-emission elements on the substrate and electrically connecting these electron-emission elements together with wiring, an electron-source substrate having a plurality of surface-conduction electron-emission elements can be structured.
By combining the above-mentioned electron-source substrate with a fluorescent substance, a display panel of an image-forming apparatus can be structured.
Up to know, such an electron-source substrate has been manufactured as follows:
A first is to form a plurality of elements each including the conductive film and a pair of the element electrodes connected to the conductive film and wiring for connecting a plurality of the elements on the substrate. Next, part of the structured electron-source substrate (at least including a forming region of the conductive film) is placed into a vacuum chamber. Then, after the vacuum chamber is evacuated, a voltage is applied across the elements via a probe and the wiring so as to form a crack on the conductive film of each element (referred to as forming below). Thereafter, gas containing an organic material is introduced into the vacuum chamber, and a voltage is again applied across each element under a desired gas partial pressure of the organic material so as to deposit carbon or a carbon compound at the end of the crack (referred to as activation below).
Japanese Patent Laid-Open No. 2000-311594, as shown in FIG. 10, discloses that a sealed atmosphere is formed with a substrate and a container covering the substrate, and a conductive film arranged on the substrate is electrified (forming and activation processing).
Referring to FIG. 10, numeral 1010 denotes a substrate; numeral 1011: a support unit; numeral 1012: a vacuum container; numeral 1015: a gas inlet; numeral 1016: an outlet; numeral 1018: a sealing member; numeral 1019: a diffusion plate; numeral 1020: a heater; numeral 1021: hydrogen or organic material gas; numeral 1022: carrier gas; numeral 1023: a water-removal filter; numeral 1024: a gas-flow control unit; numerals 1025a to 1025f: valves; numeral 1026: a vacuum pump; numeral 1027: a vacuum meter; numeral 1028: piping; numeral 1032: a driver composed of a power supply and a current control system; numeral 1031: wiring for connecting taking out wiring of the substrate to the driver; numeral 1033: an opening of the diffusion plate 1019; and numeral 1041: a thermal conduction member.
The support unit 1011 is for fixing the substrate 1010 with a mechanism such as a vacuum chucking mechanism, an electrostatic chucking mechanism, or a mechanical fixing jig.
To the vacuum container 1012, a vacuum pump 1026 for evacuating the container inside and a gas introducing device for introducing an organic material as gas are connected.
The substrate 1010 is arranged on the support unit 1011, and the surface of the substrate 1010 is covered with the vacuum container 1012 for evacuating part of a region including a plurality of elements formed on the substrate 1010. Thereby, a region surface having a plurality of elements formed on the substrate can be drawn a vacuum or exposed to an atmosphere under a desired pressure or partial pressure of an organic material. Furthermore, since part of each piece of wiring formed so as to connect to a plurality of the elements formed on the substrate is exposed, a desired electrical signal (potential) can be supplied to a pair of the electrodes constituting each element via a probe unit (not shown).
After completion of the activation processing, the container 1012 is removed from the substrate surface, and the substrate 1010 is further peeled off the support unit 1011 so as to have the electron-source substrate.
The manufacturing method described above has been adopted; however, in order to reduce a tact time in manufacturing the electron-source substrate and to improve electron-source characteristics, in the activation processing, it is indispensable to provide a high duty to a waveform of a voltage for being applied to each element within the gas containing an organic material.
On the other hand, from users of a recent liquid crystal display and a plasma display, a small-width frame structure is required.
Upon electrifying the electron-source substrate with a small-width frame by the electrifying method with high duty in a conventional processing within organic gas, an electron-emission element forming region (the center of the substrate) on the electron-source substrate is mainly heated so as to rise in temperature, so that cracks may be produced at an end of the electron-source substrate by a thermal stress due to a temperature difference to the periphery of the substrate.
There may be a technique for relaxing the stress by cooling the bottom surface of the electron-emission element forming region on the electron-source substrate while heating the periphery; however, since the heat is recovered in the thickness direction of the substrate, with increasing duty, the temperature difference between top and bottom surfaces of the substrate increases, so that there is a limit to the effect of stress relaxation.